Commit 3025520e authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcutorture: Use per-CPU random state for rcu_torture_timer() 



Currently, the rcu_torture_timer() function uses a single global
torture_random_state structure protected by a single global lock.
This conflicts to some extent with performance and scalability,
but even more with the goal of consolidating read-side testing
with rcu_torture_reader().  This commit therefore creates a per-CPU
torture_random_state structure for use by rcu_torture_timer() and
eliminates the lock.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
[ paulmck: Make rcu_torture_timer_rand static, per 0day Test Robot report. ]
parent 8da9a595

include/linux/torture.h

+2 −0
Original line number Diff line number Diff line
@@ -64,6 +64,8 @@ struct torture_random_state { 
	long trs_count;

};

#define DEFINE_TORTURE_RANDOM(name) struct torture_random_state name = { 0, 0 }

#define DEFINE_TORTURE_RANDOM_PERCPU(name) \

	DEFINE_PER_CPU(struct torture_random_state, name)

unsigned long torture_random(struct torture_random_state *trsp);



/* Task shuffler, which causes CPUs to occasionally go idle. */

kernel/rcu/rcutorture.c

+5 −5
Original line number Diff line number Diff line
@@ -1143,6 +1143,8 @@ static bool rcu_torture_one_read(struct torture_random_state *trsp) 
	return true;

}



static DEFINE_TORTURE_RANDOM_PERCPU(rcu_torture_timer_rand);



/*

 * RCU torture reader from timer handler.  Dereferences rcu_torture_current,

 * incrementing the corresponding element of the pipeline array.  The
@@ -1154,12 +1156,12 @@ static void rcu_torture_timer(struct timer_list *unused) 
	int idx;

	unsigned long started;

	unsigned long completed;

	static DEFINE_TORTURE_RANDOM(rand);

	static DEFINE_SPINLOCK(rand_lock);

	struct rcu_torture *p;

	int pipe_count;

	struct torture_random_state *trsp;

	unsigned long long ts;



	trsp = this_cpu_ptr(&rcu_torture_timer_rand);

	atomic_long_inc(&n_rcu_torture_timers);

	idx = cur_ops->readlock();

	started = cur_ops->get_gp_seq();
@@ -1176,9 +1178,7 @@ static void rcu_torture_timer(struct timer_list *unused) 
	}

	if (p->rtort_mbtest == 0)

		atomic_inc(&n_rcu_torture_mberror);

	spin_lock(&rand_lock);

	cur_ops->read_delay(&rand);

	spin_unlock(&rand_lock);

	cur_ops->read_delay(trsp);

	preempt_disable();

	pipe_count = p->rtort_pipe_count;

	if (pipe_count > RCU_TORTURE_PIPE_LEN) {

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